Penasterol (1, FIG. 1), an acidic steroidal metabolite closely related to lanosterol (2, FIG. 1) and possessing potent antileukemic activity, was originally isolated from Penares sp. by Cheng et al in 1988 (Cheng, J.F., J. Kobayashi, H. Nakamura, Y. Ohizumi, Y. Hirata, and T. Sasaki [1988] J. Chem. Soc. Perkin Trans.I 8:2403-2406; Kobayashi, J. and Y. Ooizurni, [1988] JP 01163196 A2 890627). The compound, together with its close analogues penasterone and acetylpenasterol, isolated from Penares incrustans, have been shown to inhibit IgE-dependent histamine release from rat mast cells (Shoji, N., A. Umeyama, S. Motoki, S. Arihara, T. Ishida, K Nomoto, J. Kobayashi, M. Takei [1992] J. Nat. Prod. 55(11):1682-1685; Takei, M., A. Umeyama,N. Shoji, S. Arihara, K. Endo [1995] J. Pharm. Sci. 84(2):228-230). The erylosides (Carmely, Y., M. Roll, Y. Loya, Y. Kashman [1989] J. Nat. Prod. 52(1):167-170; D""auria, M. V., Paloma L. Gomez, R. Riccio, C. Debitus [1992] Tetrahedron Lett 48(3):491-498; Gulavita, N. K., A. E. Wright, M. Kelly-Borges, R. E. Longley [1994] Tetrahedron Lett 35(25):4299-4302), isolated from various Erylus spp. constitute a family of glycosides of penasterol and related aglycones. Eryloside A possesses antitumor and antifungal activity, while Eryloside E is an antagonist of C5 a-receptorbinding. The penasterol tetrasaccharide formoside (Jaspars, M. and P. Crews [1994] Tetrahedron Lett. 35(41):75,01-7504) was recently isolated by Jaspars et al. from Erylus formosus. 
The subject invention pertains to a novel penasterol disaccharide, eryloside F (3, FIG. 1). Eryloside F has potent thrombin receptor antagonist activity and, furthermore, inhibits platelet aggregation. Advantageously, the compound has low toxicity against liver hepatocyte (HepG2) cells. The subject invention further concerns the use of salts, derivatives, and analogs of eryloside F. Such salts, derivatives, and analogs of eryloside F can be prepared by a person skilled in the art having the benefit of the disclosure provided herein.